A dual-flush toilet is a water-saving loo designed by eco-conscious Aussies. Unlike American toilets, which fill the bowl after flushing, Aussie loos have a cistern (tank) which fills instead. A half flush uses half the water in the cistern, a full flush uses all the water in the cistern. A half-flush is designed for number 1s, a full-flush for number 2s...or by those who use excessive amounts of loo paper. The capacity of cisterns has decreased over the years, in an attempt to decrease water usage in Aussie homes. Decades of drought (and in many cases, severe water restrictions for the past 5 years) have inspired (and forced) many Aussies to find ways of reducing the amount of water they use, and water-efficient dual-flush toilets are just one tactic employed.
American tourist in Australia for the first time: "What's wrong with the toilet? There's only a little bit of water in the bottom of the bowl."
Aussie: "The water is in the cistern."
American tourist in Australia for the first time: Blank stare equating to "what the heck is a cistern?"
Aussie: "The cistern is the tank at the top of the toilet."
American tourist in Australia for the first time: "Why is the water in there, not in the bowl?"
Aussie: "It's a dual-flush toilet. Press the little button for a half-flush (if you do number 1s), the big button for a full-flush (if you do number 2s)."
American tourist in Australia for the first time: "I don't get it."
Aussie: "We don't have water to waste on flushing crap into the sewage system, we'd rather have some left over for drinking, cooking, cleaning and bathing. Welcome to Australia."